The invention relates to the conditioning of naturally occurring layer silicates, in particular in the form of illitic raw materials with an illite proportion of more than 70% and defined fines.
Layer silicates have a particle fineness in the range of <2 μm (this value is characteristic of the grain fineness of clay minerals), whereby the actual particle finenesses can range, depending on the degree of definition of the particles, into more significantly fine areas, up to nanoscale values.
In the case of layer silicates with technically advantageous small plate structures, in general a distinction is made between two-layer silicates (kaolinite) and three-layer silicates (smectite, illite). In particular, the three-layer silicates offer defined particle finenesses. In this case, in general the smectite group types are used technically and commercially. For this group, relatively high occurrences of deposits with sufficient purity and with well-formed fineness exist. The typical swelling capacity of this special silicate structure is used for the deagglomeration, i.e., the separation of the individual particles from one another, with the aid of chemical processes.
The illite group essentially comprises the types of muscovite and mica that are used technically and commercially. Their rock-like definition requires a proper crushing process; in particular, they do not have the plastic characteristic of clay-mineral materials such as kaolinite and smectite.
Production of nanoscale particles is theoretically possible because of the smaller definition (produced by the decomposition in the development), but for practical reasons more likely cannot be used due to commercial and industrial considerations owing to the processing cost for the manufacture of sufficiently large production amounts and the high degree of chemical input required. The nanoscale value is limited, moreover, to the thickness of the small plates, while the surface area remains microscopic. Muscovite and mica are classified macroscopically in the case of mineralogical examination. Muscovite and mica of the illite group are generally direct decomposition products of the initial rock. In contrast to this, the actual clays are moved to secondary deposits. In this rearrangement, first the fine clay sediments are developed by mechanical, hydrothermal and chemical processes that form the prerequisite for nanoscale particles.
Corresponding to this particle fineness of these clays, the three-layer minerals, such as smectite and illite, are considerably finer than the two-layer minerals, e.g., kaolinite. With respect to nanoscale clay minerals, practice thus focuses on smectitic raw materials, since the latter are present in deposits that can be exploited quantitatively with adequate degrees of purity. Correspondingly finely-formed illite with higher degrees of purity, however, virtually does not occur or occurs only to a very limited extent. The general literature regarding clay minerals thus is concentrated on smectite material with respect to industrial use, in particular in the highly technical range and relative to nanoscale products.
In the prior art, reference is made to DE 100 61 232 A1, which relates to a process for production and preparation of Laist for medical applications, in particular for treatment of skin diseases. In this connection, this is the special use of a specific mineral-matter mixture that contains clay-mineral portions that can be of illitic definition, whereby the clay-mineral components are coincidentally illite, but not in concentrated form. In this connection, a clayey component that is used as a plastic matrix and that must not be deagglomerated is critical. The Laist represents an absolutely hydrogenic mineral mixture with a plurality of components, whereby clay as a defined material can have up to more than 60% sand. Here, this is a completely different raw material with basically different properties and goals of use, whose proportions of salt have nothing in common with a layer silicate. In addition, there is a significant difference in the processing with washing. The state of the prepared product as a paste represents another basic difference to a nanopowder.
DE 29 50 248 C2 relates to the production of multicomponent masses with the purpose of a homogenization of several components in a usable mass. This aim is not comparable to that according to this invention since in the case of the invention, the procedure is performed with a single component that is as pure as possible and that is to be crushed very finely into its primary components. According to this known proposal, the product is greatly wetted so that a special processing technique can be used. This processing technique uses known machines and devices such as, e.g., impact mills and classifiers. The milling fineness in this case is indicated with 90 μm, and the milling process proceeds in terms of a crushing process.
US 2002/45010 A1 relates to a special, concentrated application oriented to a synthetic material, especially the coating of surfaces. The basic material has only a very distant relationship to illite. The material base is hectorite as a clay-mineral material, and the description refers to the availability of nano-capable materials, so that logically, illite is thus also mentioned, which in practice has no corresponding application. The material hectorite is to be assigned to another group, namely the group of smectites. In this connection, this is a synthetically produced material, which, even from the standpoint of chemism, is specially oriented toward the exchange of Mg for Li, i.e., it has no relation to a pure, natural material.
EP 1 394 197 A1 relates to highly-viscous molding compounds that are suitable for the extrusion-blow-molding process and are based on thermoplastic polymers from the group that consists of polyamides, polyesters, polyether esters, polyester amides or mixtures thereof and nanoscale fillers, i.e., fillers with an average particle size in the range of <1 μm. The object to be achieved consists in making available highly-viscous molding compounds based on thermoplastic polymers that can be produced easily, are suitable for the extrusion-blow-molding process and in addition still have adequate strength at temperatures of 150-200° C. This object is achieved by highly-viscous molding compounds based on thermoplastic polymers that contain (a) nanoscale fillers in an amount of 0.5-15% by weight as well as (b) fiber-like filling materials in amounts of 5-30% by weight. The filler particles in this case have dimensions in the nanometer range, i.e., with a mean particle size of <1 μm (untreated fillers). As nanoscale fillers for the production of nanocomposites, such substances that can be added at any stage of production and in this case can be finely dispersed in the nanometer range are suitable. These nanoscale fillers are surface-treated but also are untreated fillers. The fillers are preferably minerals that already have a layer structure, such as layer silicates, double hydroxides or else graphite. The nanoscale fillers that are used in this connection are selected from the group of oxides, oxide hydrates of metals or semi-metals, in particular from the group of oxides or oxide hydrates of an element selected from the group that consists of boron, aluminum, calcium, gallium, indium, silicon, germanium, tin, titanium, zirconium, zinc, yttrium or iron. In addition, the nanoscale fillers are either silicon dioxide or silicon dioxide-hydrates. Nanoscale fillers that are in the polyamide molding compound [exist] in an embodiment as a uniformly dispersed layered material. As preferred minerals with a layer structure, layer silicates, double hydroxides, such as hydrotalcite or graphite, just like nanofillers based on silicones, silicon or silsesquioxanes, are indicated.
One skilled in the art gathers from this patent specification that basically all layer silicates are suitable but only synthetic or synthesized materials and the smectites that can swell are used for processing or are produced correspondingly in nanoscale. In this case, reference is clearly made to the necessity for chemical additives to achieve an exfoliation in a later manufacturing process. The basic delineation relative to this invention with respect to starting material, processing and properties follows from the above.
Further, in this patent specification, the nanoscale values are again indicated in a size range of, on the average, <1 μm. The material according to the invention is specified with an above-average value of <300 nm (0.3 μm) or with D50<150 nm (0.15 μm). That is to say, in terms of the nanoscale level, the material according to the invention differs from the prior art relative to natural mineral layer silicates by almost a full order of magnitude.
For the applicant and inventor of this application, it turned out, based on the corresponding previous works, that a desired mineral material with a layer structure would essentially have to meet the following requirements and exhibit the following properties:                a) The suitability for the production of a nanoproduct,        b) The achievement of an end product based on a natural raw material,        c) The property of a layer silicate with a three-layer structure, which in particular has no swelling capacity or in any case little swelling capacity,        d) A complete deagglomeration capability in the manufacture of products,        e) The processibility and conditioning without preliminary heat treatment,        f) The processing without the use of chemical or synthetic processes.        